The present invention relates to a substrate processing apparatus for handling a substrate such as a liquid crystal panel or semiconductor wafer; and, in particular, to an inspection apparatus for measuring or inspecting the operating accuracy or state of a substrate transfer robot employed within the substrate processing apparatus.
A single-wafer-processing multi-chamber type semiconductor manufacturing apparatus comprises a transfer chamber and a plurality of process chambers disposed thereabout, and is configured such that individual semiconductor divices can be manufactured and processed in a consistent atmosphere. In such a semiconductor manufacturing apparatus, a wafer transfer robot disposed within the transfer chamber usually transfers a semiconductor wafer (hereinafter referred to as xe2x80x9cwaferxe2x80x9d) into or out of each process chamber.
A typical conventional wafer transfer robot is constituted by a thin planar blade for horizontally holding a wafer, and an arm assembly comprising a link mechanism adapted to horizontally expand/contract and rotate while supporting this blade.
For transferring a wafer into or out of the semiconductor manufacturing apparatus without opening the inside of transfer chamber and process chamber to the outside air, a load-lock chamber is connected to the transfer chamber. A wafer cassette for accommodating a plurality of wafers at predetermined intervals in the vertical direction is set within the load-lock chamber. The wafer cassette is supported on a cassette stage in an aligning apparatus known as a cassette indexer and is vertically moved up and down. As a consequence, a selected wafer within the wafer cassette can be aligned with respect to the blade of wafer transfer robot, whereby the wafer can be accommodated and taken out.
The wafer cassette has a box shape having at least one open side face, whereas a pair of side plates opposing each other are formed-with slots for accommodating the wafers at predetermined intervals in the vertical direction. Each slot is formed so as to become parallel, e.g., usually horizontal, to the upper face of cassette stage when the wafer cassette is mounted on the cassette stage. The vertical interval between slots has such an extent that it is slightly greater than the maximum thickness of blade so as to be able to accommodate a large number of wafers, while being set such that the blade does not come into contact with the accommodated wafers when the blade is horizontally advanced so as to be inserted into the wafer cassette.
The blade of wafer transfer robot and each slot of wafer cassette, i.e., the upper face of cassette stage in the cassette indexer, should be horizontal to each other, and should be parallel to each other even if not completely horizontal. However, there are cases where the parallelism between the robot blade and the upper face of cassette stage is lost due to manufacturing errors or assembling errors in the apparatus. Therefore, a calibration operation for adjusting the degree of parallelism between the upper face of cassette stage and the robot blade to a value within a permissible range has conventionally been carried out periodically or as required.
Since the conventional calibration operation is based on visual inspection, it may yield large errors and thus cannot be carried out accurately. Since the vertical interval between the upper and lower slots is relatively narrow, there may be obstacles when taking out or accommodating wafers if an error is generated in the degree of parallelism of blade with respect to the upper face of cassette stage.
Also, depending on the state of assembly of wafer transfer robot or its state of use over a long period of time, the blade may generate sagging (downward flexure in its leading end portion), or vertical movement and sidewise rolling (collectively referred to as shaking) when linearly moved. If such xe2x80x9csaggingxe2x80x9d and xe2x80x9cshakingxe2x80x9d become too large, then the leading end of blade and the wafer may detrimentally come into contact with each other when the blade is inserted into the wafer cassette in order to take out the wafer, for example. Therefore, inspections are periodically carried out so as to determine the state of soundness of the wafer transfer robot, and maintenance operations such as adjustment and replacement of parts are carried out if the wafer transfer robot is determined defective. This inspection has conventionally been problematic in that appropriate determination cannot be carried out since it is also based on visual inspection.
Such problems similarly exist not only in multi-chamber type semiconductor manufacturing apparatus comprising a wafer transfer robot, but also in substrate transfer robots for other substrate processing apparatus for transferring a substrate such as a liquid crystal panel mounted on a blade.
In view of the circumstances mentioned above, it is an object of the present invention to provide an inspection apparatus which can accurately measure the operating accuracy or state of a substrate (wafer) transfer robot and can appropriately inspect the state of soundness of the substrate transfer robot.
In order to achieve the above-mentioned object, the present invention provides an apparatus for inspecting a substrate transfer robot having a substantially horizontally movable blade on which a substrate rests for transferring the substrate within a substrate processing apparatus such as a multi-chamber type semiconductor manufacturing apparatus, the inspection apparatus comprising a noncontact type distance sensor adapted to measure a vertical distance between a substantially horizontal reference surface within the substrate process chamber and the blade moving above the reference surface.
In this configuration, since the vertical position of blade with respect to a predetermined reference surface can be measured by the distance sensor, the sagging and shaking of the blade can be inspected.
Preferably, the distance sensor is attached to a holder mounted on the reference surface. As a consequence, the inspection apparatus can be taken out from the substrate processing apparatus while processing the substrate, whereby there is no need for modifying or improving the substrate processing apparatus.
If two or more distance sensors are arranged in parallel along a predetermined locus in which the blade advances linearly, then the vertical movement of blade can be verified. If three distance sensors are arranged in each of two rows parallel to each other along the predetermined locus in which the blade advances linearly, then the sidewise rolling or warp of the blade can be seen.
Preferably, the inspection apparatus in accordance with the present invention further comprises display means for displaying distance data measured by the distance sensor.
If the inspection apparatus in accordance with the present invention comprises blade position detecting means for detecting a horizontal position of the blade, then it can automatically determine the state of substrate transfer robot according to thus obtained data and the distance data measured by the distance sensor.
The substrate processing apparatus to which the present invention is applicable includes the multi-chamber type semiconductor manufacturing apparatus, i.e., one comprising a transfer chamber in which a substrate transfer robot is disposed; a process chamber connected to the transfer chamber, for processing a semiconductor wafer as the substrate; and a load-lock chamber connected to the transfer chamber and arranged with a wafer cassette for accommodating a plurality of semiconductor wafers. Preferably, in such a multi-chamber type semiconductor manufacturing apparatus, the reference surface is the upper face of a cassette stage of a cassette indexer disposed in the load-lock chamber.
The above-mentioned object and other characteristics and advantages of the present invention will be clear to those skilled in the art if they read the following detailed explanations with reference to the accompanying drawings.